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Refrigerated container
with the refrigeration units visible]] A refrigerated container or reefer is an intermodal container (shipping container) used in intermodal freight transport that is refrigerated for the transportation of temperature sensitive cargo. While a reefer will have an integral refrigeration unit, they rely on external power, from electrical power points at a land based site, a container ship or on quay. When being transported over the road on a trailer they can be powered from diesel powered generators ("gen sets") which attach to the container whilst on road journeys. Some reefers are equipped with a water cooling system, which can be used if the reefer is stored below deck on a vessel without adequate ventilation to remove the heat generated. Water cooling systems are expensive, so modern vessels rely more on ventilation to remove heat from cargo holds, and the use of water cooling systems is declining. The impact on society of reefer containers is vast, allowing consumers all over the world to enjoy fresh produce at any time of year and experience previously unavailable fresh produce from many other parts of the world. Cryogenic cooling Another refrigeration system sometimes used where the journey time is short is total loss refrigeration, in which frozen carbon dioxide ice (or sometimes liquid nitrogen) is used for cooling. The cryogenically frozen gas slowly evaporates, and thus cools the container and is vented from it. The container is cooled for as long as there is frozen gas available in the system. These have been used in railcars for many years, providing up to 17 days temperature regulation. Whilst refrigerated containers are not common for air transport, total loss dry ice systems are usually used. These containers have a chamber which is loaded with solid carbon dioxide and the temperature is regulated by a thermostatically controlled electric fan, and the air freight versions are intended to maintain temperature for up to around 100 hours. Full size intermodal containers equipped with these "cryogenic" systems can maintain their for the 30 days needed for sea transport. Since they do not require an external power supply, cryogenically refrigerated containers can be stored anywhere on any vessel that can accommodate "dry" (un-refrigerated) ocean freight containers. Redundant refrigeration Valuable, temperature-sensitive, or hazardous cargo often require the utmost in system reliability. This type of reliability can only be achieved through the installation of a redundant refrigeration system. A redundant ISO container system consists of a standard ISO container (i.e. intermodal container), integral primary and backup refrigeration units, and integral primary and back-up diesel generator sets. The two sets of refrigeration units are mounted on one end of the ISO container used for intermodal shipping. This is a much more usable design than others which may try to have equipment on each end and load from the side of the container. The refrigeration units (and generator sets) will be electrically interlocked for automatic start and stop operation as required, such that only one can operate at a time to maintain the required temperature set points. Should the primary refrigeration unit malfunction, the secondary unit would automatically start. Refrigeration units with more highly reliable scroll compressors can also be used in order to maintain the desired temperatures. The two sets of fuel-powered generator sets will power their respective refrigeration unit whenever necessary. The primary generator set will start automatically based on the status of the cord-supplied electrical power. If the primary generator engine cannot start after a pre-set time, the secondary generator will automatically start. See also * Refrigeration * Reefer (ship) * Refrigerator car * Refrigerator truck References Refrigerated container - Contenedores reefer Category:Freight equipment Category:Intermodal containers Category:Port infrastructure Category:Trailers